'Dagger Penises' Cause Early Death of Female Bugs

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Violent sex is taken to an extreme in warehouse pirate bugs,
where the male uses his daggerlike penis to break though the
female's body wall and insert sperm directly into her abdomen.
Now researchers have found that after enduring bouts of traumatic
insemination, the females live fast and die young.

Those female warehouse pirate bugs take advantage of what life
they have left and produce more eggs quicker than other pirate
bugs.

"These multiply mated females died at a significantly younger
age, but they started laying eggs earlier and at a higher rate to
compensate," study researcher Thomas Cameron, of Umeå University
in Sweden, told LiveScience in an email. "I would say it's not
quite right to say that
multiple mating is good for females, but it is something that
they have evolved to deal with."

Though the warehouse pirate bug may be able to mate normally
(inserting the penis into the female's reproductive tract), they
seem to have ditched this for the traumatic type of mating,
Cameron said.

That's a seemingly odd choice, since
dagger-penis mating is dangerous: Traumatic insemination
leaves gaping, seeping wounds on the female. The researchers
wondered if this
dangerous mating habit affected the female's life span or
reproductive ability.

So they tested three groups of 21 female warehouse pirate bugs in
the lab. The first group spent the day with a dead male bug, and
stayed virgins. The second group mated with one male, and the
third group mated with three males.

The females then lived their lives out in the lab under the
researchers' watchful eyes. All of the mated females had a
similar number of offspring, but the females that mated with the
three males laid their eggs quicker and died earlier. [ The
Weirdest Animal Penises ]

The researchers think multiple matings may signal the females to
lay more eggs every day, or the females could be injured from the
dagger penises and worried about dying, so they laid more eggs
earlier. The singly mated females could have also been waiting
for more suitors to take a stab before laying their eggs.

Though their sex acts may seem scary, the warehouse pirate bug is
important in keeping grain pests under control.

"It is quite a cool little beastie," Cameron said. "It is very
adept at preying on immobile
insect eggs, but when it gets the chance it pierces a moth or
beetle larvae with this venom as then the prey crawls off and
dies. The venom starts digesting the structure of the prey's body
and the bug seeks it out and has a drink."

The study will be published tomorrow (May 9) in the journal
Biology Letters.